Electromagnetic recording arrangement for acoustic vibrations



C. STILLE Feb. 23, 1932.

File dApriI 12, 1929 lll llltilrlf I l IIIIIIII Inventor: C S-fr/A Z oi the film band.

Patented Feb. 23, 1932 CURE. STILLE, 0F BERLIN,

GERMANY, assrouon T0 TELEGmHIE-PATEN -SYNDIKAT o. Ill. 3. BL, or BERLIN; GERMANY ELEGTROMAGNEEIU RECURDING- ARRANGEMENT FOR ACOUSTIG VIBRATIONS Application allied spril 12, 19%, serial No. 354,685, and in Germany September as, 1928.

It has "lready been proposed to record acoustic signals on was cylinders. The length. of the recording period is strictly limited by the length and circumference of the was 0; linders. it has also been proposed to recor acoustic signals onwax discs for the purpose of making the so-called gramophone discs. the disadvantage that the recording period is strictly limited as regards time. The case is more favourable when recording on a film band (tone film) by means of light vibrations. But even in this instance the length of the recording period is limited by the length The conditions are still more favourable when electro-magnetically recording acoustic signal on av steel wire, as considerably greater quantities of this steel wire can he reeled up than, for instance, of a But even in this case there are limits, as the inertia out a wire reel, which has till speed or" travel of from 245 metres per second in order to ensure perfect recording, is so great that particularly complicated arrangements are required for ensuring the reliable operation of such recording apparatus.

The conditions are similar as regards reproduction. Eitarting with magnetically fined records, which are to be reproduced, hitherto steel discs, steel wires, or steel bands have been used as the record carrier. Steel discs have been used for simple experimental apparatus, but for various reasons it has been impossible to obtain satisfactory results with the steel discs in practice. The reasons for this are as follows lFor magnetizing the steel discs, it is obviously only possible to use single pole electro-magnets, the finely pointed cores of which travel over the steel disc along a spiral line. This provides an open magnetic circuit which on the one hand is only capable of exerting a weak magnetic action, while on the other hand it causes serious magnetic dispersion and thereby very detrimentally affects the result. To this must be added, that with the relatively very high peripheral speed of the steel disc (about 2 ms. per second), it is very dithcult to obtain a' uniform and vibrationless guiding of the small electro-magnets over the lin this case also, however, there is steel disc, thus making it dificult to obtain electro-inagn etic recording which is entirely free from vibration. For this reason the use of steel. discs may be ruled out for practical purposes, more particularly in cases where, for the purpose under consideration, the mag netic records have tobe reproduced with great amplification. I l

JVhen steel wire is employed as the record carrier, the conditions are much more favourable in every respect. Electromagnets with a closed magnetic circuit may be used and sui able means may be employed for causing the wire to travel smoothly past the magnet cores. Hence, it has been possible to construct apparatus which may be said to work in a very satisfactory manner. For purely mechanical reasons, however, it has been found particularly dilhcult in such machines to cause the hard steel wire to be drawn through'in a perfectly reliable manner and at the requisite speed between the cores of the small electromagnets, for in practice it is absolutely essential toprevent the wire becoming entangled and the separate layers slipping over one another due to the sudden pull of the motor, thereby causing the apparatus to come to rest oreven causing the wire to break, which simply made the use of such apparatus impossible in practice.

The applicant has constructed an apparatus, the construction of which is protected by a number of patents and which is used mainly as a dictating apparatus. The applicant having also succeeded in recording and reproducing artistic performances, music, and the like, in a perfect manner, it would appear to be obvious to use such constructions for the purposes mentioned above, but there are a number of pertinent reasons to use other constructional forms for such apparatus which, to put it shortly, replace the well-known disk gramophone of to-day.

An electro-magnetic gramophone is intended 'for the use of the general public and must therefore be as simple as possible as regards its construction and operation, at any rate, not more complicated than the gramophone with sound disc now in common use. The question of price also plays a great part and the record carrier must, as regards handiness and reliability in operation hear every comparison with the sound disc as at present used.

An arrangement is described below which enables records of any length to be made electro-magnetically in an exceedingly simple and reliable manner and also to be reproduced in the simplest and most reliable manner, which, as regards the constructional simplicity both of the apparatus itself and of the record carrier, favourably compares with the ordinary talking machines.

lhe essential feature oi the arrangement according to the invention consists in this that the carrier "for recording and reproducing the acoustic vibrations is neither a steel disc nor a steel wire, but a relatively thin steel tube or a steel bar, which, both when recording and reproducing, has a rotary motion imparted to it and along which the recording or the reproducing electromagnet is caused to travel by means of a leading screw, so that the electro-magnetic waves are traced helically on the carrier or the waves traced helically on it excite the talkinghead (magnetic system) which is caused to travel along it axially.

The arrangement is preferably such that two such carriers, (steel 'bar or steel tube) are mounted in the apparatus in such a manner that first a carrier 1 is put in rotation, the peripheral surface of which is swept over by the recording magnet. Before the steel bar 1 is completely traversed, the steel bar 2 is put in motion, the recording magnet, aiter completely traversing the steel bar 1, being transferred by a change-over device to the steel bar 2, so that the recording operation proceeds without a pause on the steel bar 1 and the steel bar 2. While the steel bar 2 is being recorded on, the steel bar 1, which for this purpose is mounted in the recording or reproducing apparatus, so as to be readily removable therefrom, can be easily replaced, so that in this constructional form of the recording or reproducing'apparatus uninterrupted recording or reproduction can be carried out. 1

In Figure 1 of the accompanying drawings, a recording arrangement according to the invention is shown diagrammatically, Figures 2 and 3 being an end view and a side elevation of a portion of a reproducing apparatus.

In the accompanying drawings, M is the recording microphone which, by means of the amplifying arrangement V excites the recording magnet A. 1 and 2 are the two exchangeable steel bars, along which the recording magnet A is caused to travel by means of the spindles 79 and 19 on the guiding bar 6. For the sake of clearness, the

changeover devices which eilect the swinging over of the recording magnet to the steel bar 1 or 2 are omitted. The starting and stopping means for operatin the steel ars 1 and 2 are also omitted. These devices are controlled by the traversing means of the recording magnet on the guiding bar 5.

In Figure 1, two leading screws 17 and 10 are shown of which p pushes the recording magnet on the steel bar 1 from the left to the right, while the leading screw p pushes the recording magnet on the steel bar 2 from the right to the left. A single reversible leading screw may, of course, be used instead. Similarly, instead of rocking the recording magnet on to the steel bars 1 and 2 means may be provided for pushing two or more steel bars or tubes successively under the cores of the recording electromagnets.

For enabling the steel bars or steel tubes for the reproducing or recording carrier to be inserted in the apparatus, they are provided at one end with a point which acts as a bearing centre while the other unpointed end is provided with a groove in which a rib on the driving shaft of the apparatus engages, whereby the rotary motion is transmitted from the driving shaft to the recording or reproducing carrier.

According to Figures 2 and 3 of the drawings, 1 and 2 are the steel bars forming the reproducing carriers. On the reproducing apparatus being put in operation, the steel bar 1 is first caused to rotate and the talkipg head A is caused by-the leading screw 6 and the guiding bar a to slide along the steel bar 1. Before the talking-head has reached the end of the steel bar 1, the steel bar 2 commences to rotate. The release of this steel bar is efifected by small mechanical controlling device, which for instance is operated through the talking-head in sliding along the guiding bar a releasing a small detent which allows the mechanism for rotating the steel bar 2 to come into operation. When the talking-head has reached the end of the guide bar, the mechanism for rotating the steel bar 1 is brought to rest by a mechanical controlling device, the talking-head A being at the same time rocked over on to the steel bar 2, so that it will slide in the opposite direction on the steel bar 2. In the meantime, the steel bar 1 may be exchanged and, after the talking-head has reached the end of the steel bar 2, the changing-over operation is repeated in exactly the same way, as described with reference to the changingover of the talking-head from the steel bar 1 to the steel bar 2. In this way very long pieces of music may be played without any interruption in the performance.

The apparatus may, of course, also be so constructed that the two steel bars run continuously, the talking head only being rocked over to one or the other steel bar. In this case the controlling device for starting or stopping one or the other steel bar would be reeaeei superfluous. ifhis is a question of the amonnt of available power for driving the apparatus, which may, of course, be smaller it only one steel bar runs at a tiime. In the apparatus already constructed, which make use of a steel wire as the record cerrier, only an electric motor can he used for providing the driving power, as the reliable starting of two wire reels or relatively great weight reqniresa My fairly high driving energy. When thin steel bars are used as the record carrier, the consumption of energy is so small that ordinary spring-driven motors, such as are, for instance, used for driving the Well-known discv to talking machines, may be employed, which has the further advantage of cheapness and reliability in operation.

In the accompanying drawings a constructional form or the invention is illustrated,

in which two rotary steel bars are provided, which are played alternately, such that the tallringhead rocks alternately from one steel bar to the other. The same efiect could, of course, he ohtained by providing a magazine iv for two or more steel loars, which would advance by the distance hetween one her and the next each time a steel her has heen played {similar to the magazine oi? a revolver). lin so an arrangement, the talking-head need. not i rocked. the steel hers being: brought r another under the tallring head. lln c nstrnctional term shown two leading an Z5 are provided, of which W e ing-head from the left to the t 50m the right the left. A e leading screw only may, or? course, he .-ded., the direction of rotation of which re'zersetl hy reversing device.

claim:

electromagnetic recording and reproducing apparatus comprising a pair of parolespaced steel hare, eech loar losing of considerahly greater length than diameter provide recording and reproducing carriers, guiding har, a reproducing or recording magnet, a supporting memloer for the magnet movable on the guide bar, a pair of lead screws, means forshifting the supporting memher for alternate engagement wit the lead screws to cause the magnet to alterengage said thin bars and more the same longitudinally thereof.

in testimony whereof l have signed my name to this specification.

oner ermine. 

